Processing vulcanizable elastomers with nitrosoarylaminomethylimides



3,036,051 PROCESSING VULCANIZABLE ELASTOMERS WITHNITROSOARYLAMLNOMETHYLEMIDES John J. DAmico, Nitro, W. Va., assignor toMonsanto Chemical Company, St. Louis, Mo., a corporation of Delaware NoDrawing. Original application Sept. 30, 1957, Ser. No. 686,855, nowPatent No. 2,927,930, dated Mar. 8, 1960. Divided and this applicationSept. 29, 1958, Ser. No. 767,076

4 Claims. (Cl. 260-853) The present invention relates to processingvulcanizable elastomers with nitrosoarylaminomethylimides and moreparticularly to reacting vulcanizable elastomers with the aforesaidcompounds at elevated temperatures.

It has long been known that nitroso mixed aromatic aliphatic amineshaving a nitroso substituent on the aromatic ring have useful propertiesin the industrial arts but these compounds are of limited thermalstability. The optimum stability is apparently achieved by selectingmethyl as the aliphatic substituent but thermal stability is stillmarginal. However, it has now been discovered that substitution of ahydrogen atom on the methyl group by a radical derived from an imideincreases thermal stability.

The new compounds may be regarded as derivatives of N-methyl .C-m'trosoaromatic amines in which nitrogen replaces the hydrogen in its methylgroup to provide a structure in which two nitrogen atoms are linked by amethylene group, one nitrogen being further linked to a nitrososubstituted aromatic group and the second being part of an imide ring,the methylene group replacing imidohydrogen. By an imide ring is meant astructure in which the nitrogen is part of two acid groups which acidgroups are connected to form a closed ring. It will be noted that imidois not used synonymously with imino but is used in its usual and morerestricted sense to mean a structure in which the nitrogen is part of anacid group.

An imide may be defined as a compound derived from acid anhydrides inwhich oxygen is replaced by nitrogen. In conformity with this definitionthe amide nitrogen in the compounds of the present invention may belinked to C=O or C=S groups, these being residues of acid groups afterremoval of OH. Furthermore, the manner in which the residues of the twoacid groups are connected significantly influences the properties. Theyare preferably connected through two carbon atoms which are part of anaromatic ring. missible in either or both aromatic rings, particularlyhalogen, lower alkyl, lower alkoxy and nitro substituen'ts.

It is evident from the foregoing that one valence of the amino nitrogenis satisfied by methylene and a second valence by a nitro substitutedaromatic radical. The remaining valence may be satisfied by hydrogen ora nitroso group or by an organic substituent, as for example, aikyl,cyanoalkyl, carboalkoxyalkyl or carboxyalkyl. The radicals are listedessentially in order of decreasing preference.

In general, presence of an organic substituent reduces reactivity of thecompounds towards elastomers.

Compounds typical of the new class comprise N-(p-nitrosoanilinomethyl)-maleimide, N- 3-methyl-4-nitrosoanilinomethyl phthalimide, 4-nitro-N-(p-nitrosoauilinomethyl) -phthalimide,

Further substitution is perttes Patent ice The new compounds may beprepared by reacting the corresponding bases with nitrosating agents.The bases' required as intermediates are either known compounds or maybe prepared in known manner from the imides. A

method described by Sachs, Ber. 31, pp. 3232, 3235 (1898) is suitable.According to this method an imide is preliminarily reacted withformaldehyde to. produce an imido-oxy-methylene compound which isconverted to the corresponding halide and further treated with theamine. The imido-oxy-methylene compound may be reacted direc'tly withthe aromatic amine in which case water is removed from the reaction as aby-product in place of the hydrogen halide split off when employing themethod of Sachs. See Winstead et al., J. Am. Chem. Soc. 77, 1913 (1955)and Heine et al., ibid, 78, 672 (1956) for suitable intermediates andmethods for their preparation. The imido-oxy-methylenes form readily byreacting form- A typical preparation is dealdehyde with an imide.scribed in Example 1.

The new compounds form salts with strong inorganic acids and metal saltsand form metal salt complexes. These derivatives are also useful and areencompassed by the present invention. Salts of such acids ashydrochloric and orthophosphoric may be prepared by methods previouslydescribed for preparation of salts of nitrosoaryl amines. Metal saltsare formed by adding a soluble salt of the desired metal to an aqueoussolution of the nitrosoamine. Metallic salt complexes may be prepared byreacting nitrosoaryl amine in solution in an organic solvent with asolution of the metal salt. Some metal salts which may be cited asexamples are CuCl FeCl NiCl AgCl CdCl M11014 and CaCI EXAMPLE 1 N p-Nitrosoanilinomethyl Phthalimide To a stirred suspension of 147.2 grams(1.0 mole) of phthalimide in 1000 ml. of ethyl alcohol is added in oneportion 108 grams (1.23 moles) of 37% formaldehyde. The stirred mixtureis brought to reflux (80 C.) and 105 grams (1.13 moles) of aniline addedin one portion.

The mixture is stirred and heated atrefluxing tempera After cooling to10 C.

ture (7580 C.) for one hour. the yellow solid. which had precipitated isseparated by filtering from solution, washed with water and air dried toobtain 241 grams (95.3% yield) of N-anilinome-thyl phthalimide, M.P.143-144 C. Substitution of 800 ml. of water for 1000 ml. of ethylalcohol in the foregoing procedure and heating at -1'00 C. for one hourgives slightly higher yield of the same product.

To 439 grams of a 41.7% solution of hydrogen chlo--- ride in methylalcohol moles) is added at 5 C. 126

grams (0.5 mole) of anilinomethyl phthalimide. After removed after whichthe temperature rises to 25 C. in

one hour. Stirring is continued for 4 hours at 25-40 C. The temperaturereaches 40 C. after 3.5 hours, then slowly declines to 25 C. The mass isthen added to. 1500 grams of an ice-Water mixture. Concentrated ammoniumhydroxide is added to the batch at 510 C. until a. pH of has beenreached. Stirring is continued at 5-10 C. for one additional hour. Thegreen'solid which has'formed is filtered, washed with a literof waterand air dried. There is obtained 140.5 grams, essentially quantitativeyield, of the desired product, M.P. 183-185. C. The product purified byrecrystallization melts at 185-187 C. Below is the analysis as comparedto the values calculated for C H N O If desired the intermediateN'-nitroso compound may be isolated. A glass reaction vessel is chargedwith 25.3 grams (0.1 mole) of anilino-methyl-phthalirnide and 340 ml. ofethyl alcohol. The charge is stirred and heated to 70 C. for a fewminutes and then cooled to 5 C. There is then added in one portion 12ml. of concentrated hydrochloric acid and '8 grams (0.117 mole) of 97%sodium nitrite dissolved in 12 ml. of water. An exothermic reaction setsin causing a temperature rise from 5 to 20 C. After stirring at 20 C.for one hour, 200 ml. of water is added and stirring continued forone-half hour. The precipitate is filtered, washed with water untilneutral to litmus and air dried at 2030 C. N-(NNitrosonalinomethyl)phthalimide is obtained in a yield of 96.1%, MQP.

151154 C. After recrystallization from benzene the M.P.-is 154-156" C.Analysis gives 14.64% nitrogen as compared to 14 .94% calculated for C HN O The new compounds are useful adjuvants in the heat processing ofbutyl rubber. Butyl rubber is the well rec- .ognized andcommonlycmployed generic name applied to avariety ofelastic copolymersof isobutylene and small quantities of diolefins. The diolefins areusuallyselected so to produce a final product which possesses only asmall I or after the heat treatment. v V i 7 .As illustrative of theproperties of the new compounds typical examples are admixed with 'butylrubber in the following manner: The additive is incorporated with 400grams of butyl rubber on a mill at 50 C. in a'period of 7 about twominutes. Milling is continued for five minutes,

cuttingseveral times'from each side to insure good dispersion. Themixture so obtained together with 1000 grams of butyl rubber is chargedto a pro-heated Banbur y mixer at 150? C.j The batch is mixed foroneminute at 120 p.s.i.; thereupon carbon black and 'stearic acid arepadded and mixing continued f or an'additional'nine minv imldeN-(3-bromo-4-nitrosoanilinomethyl)phthalimide- N}(l l(-imethyl-pnitrosoanilinomethyDphthal- V p utes at C. Proceeding in the mannercompositions are compounded compris ng:

described,

Parts by weight The butyl rubber is a copolymer of isobutylene andisoprene having a Mooney viscosity in the range of 61-70 C. and molepercent unsaturation in the range of 1.5-2.0, and the carbon black is amixture of 15 parts of high abrasion furnace black and 35 parts mediumprocessing channel black. Final compounding of vulcanizable stocks iseffected on a mill at 50 C. with the roll clearance set at 0.014". Fromthe Banbury 225 gram portions are blended on the back roll for 15seconds, 7.5 grams zinc oxide, 1.5 grams 2,2'-dithiobisbenzothiazole,1.5 grams tetramethylthiuram disulfide and 3.0 grams sulfur are added in2 /2 minutes. The mass is then blended two minutes on the back roll byrolling into a cylinder and passed through edgewise nine timeswith"the*mill rolls opened to 0.020". Vulcanization is effected byheating in a press 45 minutes at 144 C. (291 F.). The physicalproperties are summarized in Table I.

' TABLE I Amount of N- (3- Ohl0ro-4- nitrosoauilinomethyl)- phthalimideModulus of elasticity in lbs/in. at 300% elongation Ult. along. percentTensile at break in lbs/in.

Torsional hysteresis 2"!"999995 wagon-crowd Torsional hysteresis wasdetermined at room temperature with an apparatus which embodies atorsion pendulum. The sample of rubber tested supplies the force torestore the pendulum when it is deflected. The logarithmic decrementrofthe observed amplitude is recorded.

As further illustrative of their valuable properties, tests are carriedout employing 0.5 part by weight of the nitrosoamine per 100 parts ofbutyl rubber. The mixing, compounding, curing and testing are allasdescribed above. Theincreased-modulus and lower hysteresis as comparedto theuntreated control are evident from the data recorded below:

. "TABLE n v Torsional hysteresis Nitrosoamine Nona VN-(p-Nitrosoanilinomethyl)phthalimide 1, 340 g9 3 N(3-ehloro-4-nitrosoanilinomethyl) phthalimide.

nitrosoanilinomethyll- V Again, employing 0.5 part by weight of thenitrosoamine per 100 parts of butyl rubber and following the mixing,compounding, curing and testing described above except that the butylrubber and nitrosoamine were mixed and heated in the Banbury for threeminutes instead of one minute, the results are as follows:

TABLE III Modulus of elasti- Torsional Nitrosoamine city inhysterelbs/in. at sis elon ation of 300% None 1, 220 47N-(p-nitrosoanilinomethyl)-succinirnide 1, 650 34 [3 (3 ehloro 4-nitrosophcnyl) 3 (phthalimidomethyl)ureido] o-tolyl isocyanate 1, 550.39 a (p [3 (3 chloro -4- nitroso) -3-(phthalimid0rnethyl)ureido]-phenyll p tolyl is 0 cy an- MP 1, 550 .39 3chloro 4 nitroso N (phthalimidomethyl) carbanilide 1, 550 38 Zinc saltof N-(4-ox0-2,5-cyclo-hexadiene-l deneiminomethyl) phthalimide 1, 810 30While the preferred method of using the new compounds is to mix with theraw butyl rubber and heat before adding pigments, significantimprovements are obtained in the presence of other ingredients. Ofcourse, at least one ingredient necessary for vulcanization must beomitted during the heating period because the process may be carried outat temperatures equal or higher than vulcanizing temperatures. Asillustrative of the effect of varying the mixing procedure thenitrosoamine is added on a 50 C. mill in the manner described. In oneprocedure the mixture is charged together with additional butyl rubberto the Banbury and mixed one minute at 125 C. after which carbon blackis added. In a second procedure butyl rubber, butyl rubber admixed withnitrosoamine and carbon black are charged together to the preheatedBanbury and heated one minute at 125 C. In the third case the butylrubber and carbon black are charged to the Banbury, heated one minute at125 C. and the mixture of butyl rubber and nitrosoamine added. In eachcase the admixture of butyl rubber, nitrosoamine and carbon black aremixed and heated for nine minutes, the maximum temperature being kept at150-l60 C. by suitable cooling. Final compounding and curing are carriedout in the manner already described. The results, employing 0.5 part ofnitrosoamine, are recorded below:

TABLE IV Butyl rubber and nitrosoarnine premixed one minute at 125 0.before addition of carbon black Butyl rubber, nitrosoamine and carbonblack added together 1, 460 2, 630 550 40 N-(p-n.itrosoammethyDphthalimide. 1, 640 2, 720 480 36N-(B-chloroA-nitrosoanilinomethyl) phthalimide 1, 920 2, 820 450 24Butyl rubber and carbon black premixed one minute at; 125 0. beforeaddition of nitrosoamine None 1, 460 2, 770 550 37 N (p nitrosoani methy)phthalimide. 1, 660 2, 650 480 32 N (3-chloro 4nitrosoanilinomethyDphthal imide 1, 870 2, 770 440 23 As illustrative ofthe results with non-black fillers, butyl rubber is admixed withN-(3-chloro-4-nitrosoanilinomethyl)-phthalimide on a 50 C. mill. Themixture and a sample of butyl rubber alone are then heated four hours at150 C. in a circulating air oven. The compositions are put back on themill and fillers added to prepare compositions comprising:

Parts by weight Butyl rubber 100 Silica. 4O 40 Titanium dioxide; 35 35N-(3-chloro4-nitrosoanilinomethyl)-phthalimide 0. 5

- The compositions so prepared are returned to the oven and heated fourhours at C. Vulcanizable stocks are compounded by adding stearic acid 2,zinc oxide 5, 2,2'-dithiobisbenzothiazole 1, tetramethylthiuramdisulfide 1, and sulfur 2 parts. After curing 45 minutes the physicalproperties are as follows:

TABLE V Modulus of elasticity in Tensile at Ult.

lbs/in. at break in elong.,

elongation lbs/in. percent Controlno nitrosoarnine 250 1, 870 950 Heatedwith nitrosoamine 1, 030 1, 580 460 Butadiene-styrene copoly-mer rubber100 Carbon black 25 Zinc oxide--- 5 Saturated hydrocarbon softener 7.5Sulfur 3 2,2-dithiobisbenzothiazole 1.5

After vulcanizing by heating 30 minutes at 158 C. the following adhesionvalues are obtained by measuring pull-out with a Dillon tester.

Pull-out Nitrosoamine value in p0 unds N0ne control. 9-12 N-(p-nitrosoanilinomethyl) phthalimide 18. 5 N(3-chloro-4-nitrosoanilinomethyl) phthalimide 17. 0 N-(3-bromo-l-nitrosoanilinomethyl) phthalimidefl 15. 3 N-(N-methyl-p-nitrosoanilinomethyl) phthalimide 15. 5N-[N-ethyl-N-(pnitrosoanilino)methyl]-phtha1imide 16. 5 N -{N-(2-cyanoetl1y1) -4-nitrosoanilinomethyl]-phthalimidc 15. 6 Methyl N (pnitrosophenyl) N (phthalimido methyl) -18 alaninate 16. 5 N (3-chloro-N-dimtrosoanilinomethyl) -phthalimide l7. 0

Adhesion of nylon cord is also enhanced but to a lesser degree. However,the new compounds have the valuable property of inhibiting heatdegradation of nylon cord. The breaking strength of nylon cord is lessthan onethird the original value after heating 42 hours in an air ovenat 150 C. but the degradation is much less after dipping the cord into adispersion of one of the new nitrosoamines. Typical results are recordedbelow employing nylon cord having a breaking strength of about 32pounds.

Breaking Nitrosoamine It is intended to cover all changesand'modifications of the examples of the invention herein chosen forpurposes of'disclosure which do not constitute departures from thespirit and scope of the invention.

The present application is a division of parent application Serial No.686,855, filedSeptember 30, 1957, now Patent Number 2,927,930.

What is claimed is:

-1. The process which comprises heating within the range of about 250F.370 F. {or a time within the range of about one minute to sixteenhours vulcanizable rubbery copolymer of at least 85% isobu-tylene and asinall amount, not more than 15% of dioleiin hydrocarbon, said copolymerhaving incorporated therein a small amount of anitrosoarylaminomethylimide characterized by the structure where R is anorganic amino substituent, in which nitrogen'is linked to the methylenegroup in the brackets,

selected from the group consisting of o I 0 u g 7 1| where A representsa radical selected from the group consisting of ortho-phenylene andsubstituted orthophenylene wherein the substituents are selected fromthe group consisting of halogen, lower alkyl, lower alkoxy and nitro, Ris selected from the group consisting of hydrogen, lower alkyl,nit-roso, cyanoethyl, lower alkyl carboxy ethyl and carboxy ethylgroups, R" is selected from the group consisting of phenyl andsubstituted phenyl wherein the substituents are selected from the groupconsisting of halogen, lower alkyl, lower alkoxy and nitro, anyvulcanizing agents, if present, being present in amounts insufficient tocause vulcanization whereby the modulus of the subsequently curedproduct is increased.

2. The process which comprises heating and mixing within the range ofabout 300 F.370 F. for a time within the range of about one to twelveminutes vulcanizable rubbery copolymer of at least 85% isobutylene and asmall amount, not more than 15% of diolefin hydrocarbon, said copolymerhaving incorporated therein a small amount of ani-trosoarylaminomethylirnide characterized by the structure H N CH.N@NO

where R represents halogen, any vulcanizing agents, if present, beingpresent in amounts insuflicient to cause vulcanization whereby themodulus of the subsequently cured product is increased.

3. The process which comprises heating and mixing within the range ofabout 300 F.-370 F. for a time within the range of about one to twelveminutes vulcanizable rubbery copolymer of at least 85% isobutylene and asmall amount, not more than 15% of diolefin hydrocarbon, said copolymerhaving incorporated therein a 1a smallamount, not more than 15% ofdiolefin hydrot V carbon, said copolymer having incorporated therein asmall amount of. N-(3-chloro-4-nitrosoanilinomethyl) z phthalimide, anyvulcanizing'. agents, if present, being presentin amounts insufiicientto cause vulcanization whereby themodu-lus of the subsequently curedproduct is'increased,

References Cited in the iile of this patent, UNITED STATES PATENTS2,616,876 Rehner Nov."4, 1952 1,395,937 Baldwin July 21, 1959' HarmonIan; 27, 1942",

1. THE PROCESS WHICH COMPRISES HEATING WITHIN THE RANGE OF ABOUT250*F.-370*F. FOR A TIME WITHIN THE RANGE OF ABOUT ONE MINUTE TO SIXTEENHOURS VULCANIZABLE RUBBERY COPOLYMER OF AT LEAST 85% ISOBUTYLENE AND ASMALL AMOUNT, NOT MORE THAN 15% OF DIOLEFIN HYDROCARBON, SAID COPOLYMERHAVING INCORPORATED THEREIN A SMALL AMOUNT OF ANITROSARYLAMINOMETHYLIMIDE CHARACTERIZED BY THE STRUCTURE